X-ray apparatus



July 8, 1958 Inn/entan- HOSEMANN United States Patent X-RAY APPARATUS2,842,677. Patented July 8, 1958 Z up transformer having a secondaryproducing a high alternating voltage, an adjustable tap arranged forcooperation with the secondary of the step-up transformer so as to be atan adjustable high alternating potential, means for Rolf Hosemann,Berlim-Spandau, Germany, assignor to Licentia Patent-Verwaltungs-G. m.b. H.,- Hamburg,

Germany Application July 24, 1952, Serial No. 300,586

5 Claims. (Cl. 250-93) The present invention relates to X-rayapparatuses, and more particularly to X ray apparatuses for diagnosticpurposes and for examinations of structure.

It is an object of the present invention to provide an X-ray apparatuscombining with a maximum brightness of the image an adjustable sharpnessof drawing soas to be able to show details having a minimum extension.

applying the high alternating potential of the tap of the step-uptransformer to the cathode, the anode being grounded, a potentiometerinserted between the tap of the step-up transformer and ground, anadjustable tap cooperating with the potentiometer and connected with theintermediate electrode so as to adjust the size of the focal spot on theanode and thus the drawing sharpness of the X-ray tube, and means forcoupling the adjustable rotatable shaft arranged parallel to the firstand second It is another object of the present invention to provide anX-ray apparatus for examining the angular diffraction of highlydispersed colloid substances.

It is a further object of the present invention to provide an X-rayapparatus for macroscopical purposes which gives rather finely detailedimages.

It is still another object of the present invention to provide an X-rayapparatus 'which is suitable for the diagnosis of cracks in bones.

It is a still further object of the present invention to provide anX-ray apparatus for measuring strains of materials without damaging ordestroying the same.

It is still another object-of the present invention to provide an X-rayapparatus suitable for examining albumins, fibers and the like which arecoarsely dispersed colloids.

An X-ray apparatus according to the present invention comprises in itsbroadest aspect an X-ray tube including a cathode, an anode, and anintermediate hollow electrode arranged between the cathode and the anodeso as to direct electrons emitted by the cathode to the anode and toproduce a focal spot thereon, means for generating a heating currentflowing through the cathode sothat the same emits electrons, means forproducing a large potential dilference between the anode and thecathode, means for producing a potential difference between theintermediate electrode and the cathode being smaller than the largepotential difference produced between the anode and the cathode, andmeans for adjusting any one of said generating means, said means forproducing the large potential difierence between the anode and thecathode, and the means for producing the potential difierence betweenthe intermediate electrode and the cathode so as to obtain the maximumpermissible brightness of the focal spot produced by the intermediateelectrode on the anode.

Preferably the X-ray tube is a fine focus tube and the intermediateelectrode acts as an electrostatic lens.

In a preferred embodiment of the present invention means for producingthe large potential difference between the anode and the cathode includea high voltage potentiometer whereas the means for producing thepotential difference between the intermediate electrode and the cathodeinclude a tap cooperating with the high voltage potentiometer andconnected with the intermediate elec trode.

A preferred embodiment of the present invention comprises a stepdowntransformer having a primary and a secondary connected to the cathode,an adjustable rheostat connected in series with the primary of thestepdown transformer so as to change the heating current flowing throughthe cathode by adjustment of the rheostat, a'stepshafts, the first shaftbeing arranged centrally between the second and third shafts, a rheostatarranged along a circular arc concentric with the second shaft, a tapconnected to the second shaft and connecting the primary 7 of thestepdown transformer in series to the rheostat so as to change theheating current flowing through the cathode by adjustment of the tapconnected to the second shaft, a step-up transformer having a secondaryproducing a negative high voltage, the secondary of the step-uptransformer being arranged along a circular arc concentrio with thethird shaft, a tap connected to the third shaft and cooperating with thesecondary of the step-up transformer so as to be at an adjustablenegative high potential, means for applying the negative high potentialof the tap connected with the third shaft to the cathode, the anodebeing grounded, a potentiometer arranged along a circular arc concentricWith the first shaft and being inserted between the tap connected to thethird shaft and ground, a tap connected to the first shaft andcooperating with the potentiometer, the tap connected with the firstshaft being connected with the intermediate electrode so as to adjustthe size of the focal spot on the anode and thus the drawintermediateelectrode on the anode.

, being shiftable whereas the tap connected to the first shaft isrigidly connected thereto.

Preferably first, second and third toothed wheels are rigidly connected,respectively, to the first, second and third shafts, the second andthird Wheels meshing in one end position of the second and third shaftswith the first toothed wheel so 'as to form a disengageable couplingbetween the shafts.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with n the accompanying drawings, inwhich:

shown in a sectional side elevation and corresponding to the copendingUnited States application Serial No.

3 300,587, filed July 24, 1952, for X-ray Tube, now Patent No.2,683,223; and

Fig. 3 is a perspective view of a practical embodiment of some parts ofthe electrical accessories shown diagrammatically in Fig. 2.

Referring now to the drawings and first to Figs. 1a, b, and c, let x bea radius vector lying in the plane of the X-ray film supposed to beplane. Let Z(x) be the intensity distribution of the primary X-ray beam,crossing the film in watt/cmP, Z(x) being measured either in microscopywith no object being inserted into the path of the rays (zerophotograph) or in microscopic or diagnostic photography if the object tobe penetrated by rays is punctiform and the equivalent of a pointaperture. Particularly if the primary beam of rays in fine structurephotography is diaphragmed out infinitely finely or by other suitablemeans is made to converge on the film at the point x=0, Z(x) has theform of a point function. In microscopic photographs Z(x) is a pointfunction if the focal spot is punctiform. Therefore, the followingrelation holds:

where P(x)= for any x#0. In consequence thereof one obtains for thetotal primary intensity W which impinges on the film where d)", is asurface element of the X-ray film at the point x. Using this punctiformdistribution of the primary intensity it will be seen that the objectbrought into the path of the X-rays causes on the film a distribution ofintensity:

J(x)=W .p(x)

p(x) having the dimension GEL-2 and being a function characterizing theobject to be X-rayed or photographed. However, in the general case of afinite primary beam of rays the distribution of the intensity on theX-ray film is given by the folding product of Z and p:

In this equation y is the radius vector lying in the plane of the filmwhich starts at x=0 and ends at the surface element df The surfaceintegral (3) is to be extended over the entire area of the film.

The distribution of the intensity according to Equation 3 is blurred ina characteristic manner in comparison to the sharp image given byEquation 2. If, for instance, for X-raying of the diagram shown in Fig.1a which is a plotting of p(x) against x, a primary beam of rays havingthe intensity of distribution Z(x) shown in Fig. 1b is used, a diagramof the intensity distribution is obtained by using Equation 3 which isrepresented by the curve I (x) shown in Fig. 1c. Figs. 1a and 10 showthat the curve for J (x) copies the diffused background 1 true to shape.However, already the reflex 2, the integral width B of which iscomparable to the integral width B of the primary beam (Fig. 1b) appearsmuch distorted at 3 so that the true shape of the reflex 2 is hardlyrecognizable. The same holds even with greater force for the reflex 4having an integral width B; being small in comparison to the integralwidth B and being represented by the portion 5 of the curve in Fig.which affords no chance of analyzing the original curve 4 represented byFig. 1a. If generally B is the integral width of a reflex or cavity orany other detail of the object to be X-rayed it has been discovered thatin many practical cases a true reproduction by the image is secured ifapproximately the following relation holds:

I11 this case it can be deduced from equation that practically thefollowing relation holds:

where p,(x) is the value of the function 17(x) within the range of thereflex 1'. Since an upper limit is set to the loading capacity of thesurface of the anode of the X-ray tube by the melting point of thematerial of the anode, Z(O) cannot exceed a certain maximum value Zunder given external conditions.

Thus in Equation 5 is W Z B Thus in order to obtain a sufficientbrightness of the image B should be chosen as large as possible. Theconditions (4) and (6) to be satisfied for an X-ray tube giving sharplydrawn and bright images evidently counteract each other.

The present invention allows to obtain an X-ray tube for producing sharpand simultaneously bright images by adapting the sharpness of drawing tothe object to be photographed by choosing and simultaneously adjustingthe surface load Z, of the tube to its maximum value Z,,,:

by controlling the anode current, the heating current, the anodevoltage, or these three quantities in combination. The requirement to besatisfied by the tube and given by Equation 7 means a width of the focalspot which is variable Over a large range. For instance in many problemsof macroscopy, the wide-angle-microscopy and in diagnostics widths ofthe focal spot amounting to about 1 mm. are suificient. However, forexamining the small-angle-dispersion of highly dispersed colloidmaterials, for very finely detailed macrostructures and cracks of bonesetc., Widths of the focal spot down to 0.1 mm. are required unless amajor part of the X-ray radiation is screened off by an additionaldiaphragm which can be done of course only at the expense of thebrightness of the image. In a similar manner for many problems of themeasurement of mechanical strains of working materials by reflexphotography focal spots having a width of 0.1 mm. are required. Withcoarsely dispersed colloids such as albumins, fibers or the like evenmore narrow focal spots are required.

Referring now to Fig. 2, an X-ray tube with the electrical accessoriesthereof according to the invention is shown diagrammatically. The tubeshown in the diagram has an electrostatic lens system 9 comprising anaperture 10 as more fully disclosed in the copending United Statesapplication Serial No. 300,587, filed July 24, 1952, for X-ray Tube, nowPatent No. 2,683,223. The electrostatic lens system 9 is formed by anintermediate electrode arranged between the cathode 6 and the anode 8the active surface of which is arranged in the right-hand part of theintermediate electrode 9 which is provided with openings or windows 11for the X-ray radiation which leaves the tube through windows 12. Theindex of refraction of the lens system 9 can be changed from the outsideof the tube by controlling the potential differences between theelectrodes, viz., the intermediate electrode 9 and the cathode 6, andthe anode 8 and the cathode 6.

The heating current for the cathode 6 is supplied by the secondary of astepdown transformer 39, the primary 40 of which is connected to themains of e. g. 220 volts through a rheostat 14 with terminals 26 and 27which is tapped by an adjustable tap 18 connected to one end of theprimary 31.

A step-up transformer 32 has a primary 33 connected to the 220 voltsmains and a secondary 15 which is grounded at one end thereof whereasthe other end 29 is left open. The step-up transformer 32 generates forinstance a voltage of 50 kilovolts. An adjustable tap 17 cooperates withthe secondary 15 so that the terminal 28 connected to the tap 17 is atan adjustable high alternating potential. The terminal 28 is connectedtothe cathode and to the Wehnelt cylinder 7 surrounding the cathode. Apotentiometer 13 is inserted between the terminal 28 and the groundedanode 8. An adjustable tap 16 cooperating with the potentiometer 13 isconnected to the intermediate electrode or lens system 9.

The operation of this device is as follows:

The anode 8 of the tube is always at ground potential which can be takenas Zero. The terminal 28 has alternately positive and negativepotentials against ground and the anode 3. Furthermore the intermediateelectrode 9 has an alternating potential which is not quite as large asthe potential of the terminal 28 but always of the same sign. Theheating current supplied by the secondary of transformer 39 heats thecathode 6 to electron-emitting temperature and the electrons emitted bythe same are accelerated toward the anode 8 when the terminal 28 isnegative against ground. By impinging on the anode 8 the electronsgenerate an X-ray radiation in well known manner. i i

The brightness of the focal spot produced by the electrons on the anode8 can be controlled by the heating current supplied by the stepdowntransformer 39 and/ or the secondary voltage produced by the step-uptransformer 32. The heating current is controlled by adjusting the tap18 on the rheostat 14 where the potential differences between the anodeand cathode is'controlled by the tap 17 cooperating with the secondary15 of the step-up transformer 32. The width of the focal spot producedat the anode 8 and thus the sharpness of the image made by the X-raytube is controlled by the potential of the electrostatic lens 9 whichcan be adjusted by means. of the adjustable tap 16 cooperating with thepotentiometer 13. If, for instance, a particularly fine focal spot is tobe produced the potential of the electrostatic lens 9 is controlled bymeans of the tap 16 so that the virtual image of the glow cathode is onthe anode 8. However, if the potential of the electrostatic lens 9 ischanged with respect to the potential difference between the anode 8 andthe cathode 6 the virtual image of the latter is displaced from thesurface of the anode 3 along the aXis of the tube so that the focal spotbecomes larger.

Referring now to Fig. 3 showing a practical embodiment of the rheostat14 with the tap 18, the secondary 15 with the tap 17 and thepotentiometer 13 with the'tap 16 it will be seen that the tap 16 isrigidly secured to a first shaft 34 held in stationary bearings 35 so asto be rotatable. The potentiometer 13 is arranged along a circular arcconcentric with the first shaft 34. A knob 23 allows to turn the shaftand thereby to adjust the tap 16 with respect to the potentiometer 13. Asecond shaft 36 is arranged parallel to the first shaft34 and is axiallydisplaceable in stationary bearings 37. The second shaft 36 carries aknob 24 for rotating the same. The rheostat 14 is arranged along acircular arc'concentric with the second shaft 36 and the tap 18 isconnected by a key and groove connection 31 with the second shaft 36 soas to be rotatable with the same but shiftable thereto in axialdirection so that the tap 18 always cooperates with the rheostat 14. Athird shaft 22 is arranged in stationary bearings 38 parallel to thefirst shaft 34 and the second shaft 36, the first shaft 34 beingdisposed in the central position with respect to the second shaft 36 andthe third shaft 22. The secondary 15 is arranged along a circular arcconcentric with the third shaft 22 which carries an operating knob 25.The tap 17 is connected to the third shaft 22 by a groove and keyconnection 30 similar to the groove and key connection 31. Furthermore,at the ends of the first shaft 34, the second shaft 36 and the thirdshaft 22 are arranged, respectively, a first toothed wheel 19, a secondtoothed wheel 20 and a third toothed wheel 21 meshing with one anotherin one end position of the second and third shafts36and 22 so as to forma coupling. However, the coupling can be disengaged by displacing thesecond shaft 36 and the third shaft 22 axially as indicated in dottedlines. If the coupling is engaged a rotation of one of the knobs 23, 24,25 entails a rotation of all three shafts together whereby the taps 16,17, 18 are adjusted with one operation so that the X-ray tube isautomatically controlled for maximum loading. However, if the clutch isdisengaged each tap can be individually adjusted and the heatingcurrent, the potential of the lens system 9 and the anode voltage can becontrolled separately.

If the X-ray apparatus according to the invention is to be used fordiagnostic purposes or for macroscopic examinations, the automaticcoupling should be used for controlling principally the tube voltage bymeans of the knob 25. The tube produces then a softer X-ray radiationtogether with an increase of the drawing sharpness transversely to thedirection of the rays and of the distinguishabiilty of the minimaldimensions of cavities or the like in direction of the rays. 1

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofX-ray apparatuses differing from the types described above.

While the invention has been illustrated and described as embodied in anX-ray apparatus for diagnostic purposes and for examinations ofstructure, it is not intended to be limited to the details shown, sincevarious modifications and structural changes may be made withoutdeparting in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. An X-ray apparatus comprising, in combination, an X-ray tubeincluding a cathode, an anode, and an intermediate hollow electrodearranged between said cathode and said anode so as to direct electronsemitted by said cathode to said anode and to produce a focal spotthereon; a stepdown transformer having a primary and a secondaryconnected to said cathode; an adjustable rheostat connected in serieswith said primary of said stepdown transformer so as to change theheating current flowing through said cathode by adjustment of saidrheostat; a step-up transformer having a secondary producing a highalternating voltage; an adjustable tap arranged for cooperation withsaid secondary of said stepup transformer so as to be at an adjustablehigh alternating potential; means for applying said high alternatingpotential of said tap of said step-up transformer to said cathode, saidanode being grounded; a potentiorneter inserted between said tap of saidstep-up transformer and ground; an adjustable tap cooperating with saidpotentiometer and connected with said intermediate electrode so as toadjust the size of said focal spot on said anode and thus the drawingsharpness of said X-ray tube; and means for coupling said adjustable tapof said potentiometer with said adjustable rheostat and said adjustabletap of said secondary of said step-up transformer so as to obtain themaximum permissible brightness of the focal spot produced by saidintermediate electrode on said anode.

2. An X-ray apparatus comprising, in combination, a fine focus X-raytube including a cathode, an anode, and an intermediate hollow electrodearranged between said cathode and said anode and acting as anelectrostatic lens so as to direct electrons emitted by said cathode tosaid anode and to produce a focal spot thereon; a stepdown transformerhaving a primary and a secondary connected to said cathode; anadjustable rheostat connected in series with said primary of saidstepdown transformer so as to change the heating current flowing throughsaid cathode by adjustment of said rheostat; a step-up transformerhaving a secondary producing a high alternating voltage; an adjustabletap arranged for cooperating with said secondary of said step-uptransformer so as to be at an adjustable high alternating potential;means for applying said high alternating potential of said tap of saidstep-up transformer to said cathode, said anode being grounded; apotentiometer inserted between said tap of said step-up transformer andground; an adjustable tap cooperating with said potentiometer andconnected with said intermediate electrode so as to adjust the size ofsaid focal spot on said anode and thus the drawing sharpness of saidX-ray tube; and means for coupling said adjustable tap of saidpotentiometer with said adjustable rheostat and said adjustable tap ofsaid secondary of said step-up transformer so as to obtain the maximumpermissible brightness of the focal spot produced by said intermediateelectrode on said anode.

3. An X-ray apparatus comprising, in combination, an X-ray tubeincluding a cathode, an anode, and an intermediate hollow electrodearranged between said cathode and said anode so as to direct electronsemitted by said cathode to said anode and to produce a focal spotthereon; a step down transformer having a primary and a secondaryconnected to said cathode; a first rotatable shaft; a second rotatableshaft arranged parallel to said first shaft; a third rotatable shaftarranged parallel to said first and second shafts, said first shaftbeing arranged centrally between said second and third shafts; arheostat arranged along a circular arc concentric with said secondshaft; a tap connected to said second shaft connecting said primary ofsaid stepdown transformer in series to said rheostat so as to change theheating cur rent flowing through said cathode by adjustment of said tapconnected to said second shaft; a step-up transformer having a secondaryproducing a negative high voltage, said secondary of said step-uptransformer being arranged along a circular arc concentric with saidthird shaft; a tap connected to said third shaft and cooperating withsaid secondary of said step-up transformer so as to be at an adjustablenegative high potential; means for applying said negative high potentialof said tap connected with said third shaft to said cathode, said anodebeing grounded; a potentiometer arranged along a circular arc concentricwith said first shaft and being inserted between, said tap connected tosaid third shaft and ground; a tap connected to said first shaft andcooperating with said potentiometer, said tap connected with said firstshaft being connected with said intermediate electrode so as to adjustthe size of said focal spot on said anode and thus the drawing sharpnessof said X-ray tube; and means for coupling said shafts with one anotherso as to obtain the maximum permissible brightness of the focal spotproduced by said intermediate electrode on said anode.

4 An X-ray apparatus comprising, in combination, an X-ray tube includinga cathode, an anode, and an intermediate hollow electrode arrangedbetween said cathode and said anode so as to direct electrons emitted bysaid cathode to said anode and to produce a focal spot thereon; a stepdown transformer having a primary and a secondary connected to saidcathode; a first rotatable'shaft arranged axially undisplaceably; asecond rotatable shaft arranged parallel to said first shaft and beingaxially displaceable; a third rotatable shaft arranged parallel to saidfirst and second shafts and being axially displaceable, said first shaftbeing arranged centrally between said second and third shafts; arheostat arranged along a circular arc concentric with said secondshaft; a tap shiftably connected to said second shaft and connectingsaid primary of said stepdown transformer in series to said rheostat soas to change the heating current flowing through said cathode byadjustment of said tap connected to said second shaft; a step-uptransformer having a secondary producing a negative high voltage, saidsecondary of said step-up transformer being arranged along a circulararc concentric with said third shapt; a tap shiftably connected to saidthird shaft and cooperating with said secondary of said step-uptransformer so as to be at an adjustable negative high potential; meansfor applying said negative high potential of said tap connected withsaid third shaft to said cathode, said anode being grounded; apotentiometer arranged along a circular arc concentric with said firstshaft and being inserted between, said tap connected to said third shaftand ground; a tap rigidly connected to said first shaft and cooperatingwith said potentiometer, said tap connected with said first shaft beingconnected with said intermediate electrode so as to adjust the size ofsaid focal spot on said anode and thus the drawing sharpness of saidX-ray tube; and disengageable means for coupling said shafts with oneanother so as to obtain the maximum permissible brightness of the focalspot produced by said intermediate electrode on said anode.

5. An X-ray apparatus comprising, in combination, an X-ray tubeincluding a cathode, an anode, and an intermediate hollow electrodearranged between said cathode and said anode so as to direct electronsemitted by said cathode to said anode and to produce a focal spotthereon; a stepdown transformer having a primary and a secondaryconnected to said cathode; a first rotatable shaft arranged axiallyundisplaceably; a second rotatable shaft arranged parallel to said firstshaft and being axially displaceable; a third rotatable shaft arrangedparallel to said first and second shafts and being axially displaceable,said first shaft being arranged centrally between said second and thirdshafts; a rheostat arranged along a circular arc concentric with saidsecond shaft; a tap shiftably connected to said second shaft andconnecting said primary of said stepdown transformer in series to saidrheostat so as to change the heating current flowing through saidcathode by adjustment of said tap connected to said second shaft; astep-up transformer having a secondary producing a negative highvoltage, said secondary of said step-up transformer being arranged alonga circular arc concentric with said third shaft; a tap shiftablyconnected to said third shaft and cooperating with said secondary ofsaid step-up'transformer so as to be at an adjustable negative highpotential; means for applying said negative high potential of said tapconnected with said third shaft to said cathode, said anode beinggrounded; a potentiometer arranged along a circular arc concentric withsaid first shaft and being inserted between, said tap connected to saidthird shaft and ground; a tap-rigidly connected to said first shaft andcooperating with said potentiometer, said tap connected with said firstshaft being connected with said intermediate electrode so as to adjustthe size of said focal spot on said anode and thus the drawing sharpnessof said X-ray tube; first, second, and third toothed wheels rigidlyconnected, respectively, to said first, second and third shafts, saidsecond and third wheels meshing in one end position of said second andthird shafts with said first toothed wheel so as to form a disengageablecoupling between said shafts so as to obtain the maximum permissiblebrightness of the focal spot produced by said intermediate electrode onsaid anode.

References Cited in the file of this patent UNITED STATES PATENTS1,612,641 Morrison Dec. 28, 1926 1,949,347 Bouwers Feb. 27, 19342,053,792 Huppert et a1. Sept. 8, 1936 (Other references on followingpage) 9 UNITED STATES PATENTS 2,605,458 2 617 046 Schlesmger Sept. 27,1938 Bischofi Feb. 14, 1939 2,683,223 Kloos Jan. 20, 1942 WestandorpAug. 6, 5

Ott Nov. 28, 1950 10 Zabransky July 29, 1952 Douma et a1. Nov. 4, 1952Hosemann July 6, 1954 FOREIGN PATENTS Germany May 15, 1916

